1. Field of the Invention
The present invention relates to a thermal control for variable speed DC brushless fans, and in particular to a fan in which the variable speed is normally dependent on temperature alteration and in which the fan is operated at full speed when the thermal sensor malfunctions in order to protect computer systems and the like which require constant cooling.
2. Description of the Related Art
Computer systems have become popular auxiliary facilities in houses, factories, offices and the like where work is performed. In order to improve quality of life generally, the quality of the working environment must be improved. For example, the noise produced upon operating of a fan concerns both operators of the fan and the manufacturers. Nevertheless, fans are essential elements for dissipation of heat from computer systems and various equipment thereof. The cooling fan of the present invention is designed with these considerations in mind.
While the computer is at full load, the conventional constant speed fan is operated at full speed, but while the computer is not at full load, the conventional constant speed fan still maintains full speed operation and a high noise level. In contrast, in the cooling fan of the present invention, while the computer is not at full load and the inside temperature is low, a temperature sensor will sense the alteration of temperature and change its resistance, thereby feeding back to the control circuit a signal which slows down the speed of the fan to just accommodate the temperature range required. As a result, noise from the fan will be cut down and the service life of the fan lengthened.